Field of the Invention
The present invention relates to a near-field optical head capable of reproducing and recording high-density information using near-field light. The present invention also relates to a method of manufacturing the near-field optical head.
In recent years, a rapid development on both aspects of the hardware and the software is accomplished in the field of the information appliances and the amount of information to deal with keeps on growing drastically therewith. With regard to the information storage apparatus as one of the information appliances (HDD in particular), a rapid shift to high-density recording goes along currently in such a way that the recording capacity per unit area in recording medium increases by 60 percent in annual rate. Therefore, a further miniaturization is desired in the size of one record unit (bit) recorded and reproduced on a recording medium.
For recording or reproducing in a minute region, an apparatus for observing the minute region of a nanometer order on the surface of the sample or an application of the scanning probe microscope represented by scanning tunnel microscope (STM) or an atomic force microscope (AFM) is becoming an object of public attention. SPM scans the probe having a sharpened tip over the surface of the sample, while observing an interaction such as the tunnel current generated between the probe and the surface of the sample or the force between the atoms so as to obtain an image of a certain resolution depending on the tip configuration of the probe.
For performing a high density recording of a recording medium, the method of recording and reproducing with the use of light in comparison with magnetism has an advantage of enabling a high-density recording along the tracking direction (radial direction of the recording medium). Thus, the application of the near-field optical microscope viewing by light is expected as a promising matter especially among SPM.
The near-field optical microscope deals with an interaction produced between the near-field light generated on the surface of an inspection sample and the probe as an observation subject so as to be able to observe the minute region of the sample surface. The principle of the inspection approach is described in detail hereinafter.
The near-field light is generated by irradiating propagating light onto the surface of the inspection sample. Since the near-field light is generated only in a highly adjacent area on the surface of the inspection sample, the sharpened tip of the probe is approached closely to the surface of the inspection sample within a distance equal to or less than xcexcm so as to scatter the near-field light generated from the tip of the probe. The scattered light is guided through a small aperture of the tip of the probe and processed by a conventional detection process of a transmitted light. Thus, the limitation of the viewing resolution of the conventional optical microscope is broken through and so the observation of a minute region by light becomes possible. Furthermore, a light of great intensity is introduced into the probe toward the inspection sample to generate a near-field light of high energy density in the minute aperture of the probe. By means of this near-field light, a local modification of the construction or the properties of the sample surface is also made possible. As described above, a realization of optical memory recording with high-density is thought to be possible by means of the application of near-field optical microscope.
In the architecture of the optical memory recording apparatus using such a near-field light, the probe is the most important part because it has a minute aperture acting as a recording and reproducing optical head. As an example of a probe having a minute aperture, as for instance described in U.S. Pat. No. 5,294,790, a cantilever-type photoprobe is proposed comprising an aperture penetrating through a silicon substrate by means of semiconductor manufacturing technology of photolithography or the like, an insulation film formed on one side of the surface of the silicon substrate and a cone-shaped light waveguide layer formed on the insulation film in the opposite side of the aperture. In this cantilever-type photoprobe, an optical fiber is interposed into the aperture so that the light can be transmitted through the minute aperture part which is formed by coating a light waveguide layer with a metal film except for the tip portion. Consequently, it is made easy to manufacture the aperture part.
Furthermore, an application of the planar probe without sharpened tip like the above-mentioned probe is proposed (T. Yatsui et al., xe2x80x9cReadout capability of a planar apertured probe for optical near-field memoryxe2x80x9d, NFO-5, 115, Shirahama, Dec. 10, 1998). The planar probe is the one which is provided with an aperture of reverse pyramid structure on silicon substrate by means of anisotropic etching and in particular the vertex of the aperture is perforated with a diameter of several nm to form an aperture part. A plurality of such planar probes can be made simultaneously as a lump on a same substrate by semiconductor manufacturing technology, namely making an array of the planar probes is easy and in particular the planar probe has an advantage of utilizing as a suitable optical head for recording and reproducing the optical memory using near-field light. As an optical head using this planar probe, a head having a planar probe provided on the flying head used in a hard disk drive is proposed (Nikkei Electronics, Mar. 10, 1997 issue). The flying head is conventionally designed to fly by aerodynamic design keeping a spacing of 50-100 nm above the recording medium. With the use of this flying head, keeping the head and the recording medium in an extreme proximity (positional relationship) and forming a minute aperture in the flying head at the recording medium side, it becomes possible to generate near-field light. Therefore, high-density recording and reproduction by light is thought to be possible.
On realizing the optical information memory apparatus using near-field light, the utility value of the apparatus in itself is enhanced if the device in itself is made small and slim. For making the device small and slim, it is considered suitable to adopt a structure in which the light propagated in parallel with the recording medium is turned to a direction perpendicular to the medium and the aperture with the aid of optical components. However, with this structure, the head in itself becomes large and heavy due to the combination of optical components and results in a problem that the positioning accuracy and the response characteristics is deteriorated.
In addition, when a light is launched into the aperture by means of a light waveguide path such as an optical fiber, the intensity of the near-field light emitted from the aperture becomes small resulting in problems that the recording and reproducing rate is decreased and that the reliability of the information recorded and reproduced is deteriorated. As for this problem, since the light emitted from the light emitting edge of the light waveguide path is propagated spreading its width, and so the spot diameter of the light becomes large in accordance with the distance from the emitting edge. Then, the intensity of the light irradiated on the aperture is decreased and so is reduced the intensity of the near-field light for recording and reproducing. As a result, because the ratio of light intensity responsive to the information (S/N), a problem is generated that the recording and reproducing rate or the reliability of the information is deteriorated.
Therefore, a first near-field optical head according to the present invention comprises a slider supported by a load applying suspension arm for acquiring a flying force by means of a relative motion to a recording medium to make a spacing between the recording medium in accordance with a balance between the load and the flying force, a minute structure made on the slider in the recording medium side, a light propagating medium arranged on the slider in the opposite side of the recording medium and disposed substantially parallel with the suspension arm, a mirror for directing the light emitted from the light propagating medium arranged substantially above the minute structure to the minute structure, and a path shortening structure for shortening the path between the light emitting edge of the light propagating medium and the minute structure.
Therefore, according to the first near-field optical head related to the present invention, by placing the mirror in the vicinity of the minute structure by means of the optical path shortening structure and also by setting the position of the light emitting edge of the light propagating medium close to the minute structure, the distance between the light emitting edge of the light propagating medium and the minute structure can be shortened and also the spot diameter of the light from the light propagating medium can be reduced so that the intensity of the near-field light generated by the minute structure is increased. Therefore, a near-field optical head capable of high-density recording and reproducing can be obtained.
Further, in a second near-field optical head according to the present invention, a construction is adopted in which the minute structure is a minute aperture.
Therefore, according to the second near-field optical head related to the present invention, high-density recording and reproducing is made possible, because the spot diameter of the near-field light on the recording medium is reduced to approximately the same size as the minute aperture.
Further, in a third near-field optical head according to the present invention, a construction is adopted in which the optical path shortening structure is a groove formed in the vicinity of the minute structure and the light propagating medium is arranged inside the groove.
Therefore, according to the third near-field optical head related to the present invention, the distance between the light emitting edge of the light propagating medium and the minute structure can be shortened so that a near-field optical head capable of generating near-field light of great intensity can be obtained. Furthermore, because it is easy to fix the light propagation medium by means of forming a light propagation medium in the groove, a near-field optical head capable of generating a near-field light of stable intensity can be obtained.
Further, in a fourth near-field optical head according to the present invention, a mirror is arranged on and integrated with the substrate which is placed above the slider.
Therefore, according to the fourth near-field optical head related to the present invention, a stable optical system can be constructed and the intensity of the near-field light generated by the minute structure is made stable.
Further, in a fifth near-field optical head according to the present invention, a construction is adopted in which the mirror is formed in the light propagating medium.
Therefore, according to the fifth near-field optical head related to the present invention, as the mirror and light propagating medium each of which is the component of the near-field optical head can be made integrally, the adjustment of the optical axis of the mirror and the light propagating medium becomes unnecessary and so the adjustment of the optical axis is made easy. In addition, since the number of the components is decreased, the unit price of the head becomes cheap so as to enable a provision of cheap near-field optical head.
Further, in a sixth near-field optical head according to the present invention, a construction is adopted in which the mirror has a concave shape to provide a near-field optical head that concentrates light emitted from the light propagating medium. In addition, in a seventh near-field optical head according to the present invention, the head has a lens function to concentrate the light on the tip of the light propagating medium.
Therefore, according to the sixth and seventh near-field optical head, it is possible to increase the energy density of the light in the minute structure so that the intensity of the near-field light generated by the minute structure can be increased.
Further, in the eighth near-field optical head related to the present invention, a near-field optical head is characterized in that a mirror aligning mechanism is formed on the slider and/or the substrate provided with the mirror to set the mirror and the minute structure in position.
Therefore, according to the eighth near-field optical head, the optical adjustment to maximize the intensity of the near-field light generated by the minute structure is made easy.
Further, the ninth near-field optical head related to the present invention has a construction in which a groove or a protrusion for fixing the optical components for launching the light on the light propagating medium is formed on the mirror substrate.
Therefore, according to the ninth near-field optical head, the light is launched on the light propagating medium effectively so that the intensity of the near-field light generated by the minute structure becomes large.
Further, the tenth near-field optical head related to the present invention has a construction in which the light propagating medium is fixed or formed on the slider.
Therefore, according to the tenth near-field optical head, the position of the light propagating medium is made stable by means of fixing or forming the light propagating medium on the slider so that the intensity of the near-field light generated by the minute structure can be made stable.
Further, in the eleventh near-field optical head related to the present invention, a construction is adopted which is characterized in that the light propagating medium is fixed or formed on the substrate in the same side on which the mirror is formed.
Therefore, according to the eleventh near-field optical head, the position of the light propagating medium is made stable even if a slider having a small thickness is used. In addition, the use of a slider having a small thickness makes it possible to shorten the distance between the light propagating medium and the minute structure so that the intensity of the near-field light generated by the minute structure can be increased.
Further, the twelfth near-field optical head related to the present invention has a construction in which the light propagating medium is comprised such that the light incident part is fixed on the substrate and the light emitting part is fixed on the slider.
Therefore, according to the twelfth near-field optical head, the positioning of the groove or the protrusion for fixing the light incident edge of the light propagating medium and the components for light incident on the light propagating medium can be performed precisely and the light emitting edge of the light propagating medium can be arranged close to the minute structure so that the intensity of the near-field light generated by the minute structure can be increased to a greater extent.
Further, the thirteenth near-field optical head related to the present invention has a construction in which the light propagating medium is an optical fiber having a tip machined in a narrow shape by means of grinding thereof in parallel with the optical axis.
According to the construction, optical fiber with its tip sharpened makes it possible to arrange the light emitting edge of the optical fiber close to the mirror so that the spot diameter of the light emitted from the light emitting edge of the optical fiber in the minute structure can be reduced. Therefore, the intensity of the near-field light generated by the minute structure is increased.
Further, the fourteenth near-field optical head related to the present invention has a construction characterized in that the light propagating medium is a thin film waveguide.
Consequently, with the use of a thin film waveguide thinner and lighter than an optical fiber as the light propagating medium, the mass of the near-field optical head is reduced. Therefore, it becomes easy to improve the positioning accuracy or the positioning speed of the near-field optical head. In addition, by means of using the thin film waveguide as the light propagating medium, it becomes easy to make the near-field optical head in a thin shape and the apparatus can be constructed in more compact size.
Additionally, the first method for manufacturing the near-field optical head related to the present invention is a method for manufacturing the near-field optical head including a method for forming a mirror, a method for forming a slider and an assembling process of the mirror and the slider. The method for forming the mirror is processes including a forming process of the projection on the substrate, a forming process of the reflection coating on the projection and a forming process of the configuration. The method for forming the slider is processes including a forming process of the minute structure, a forming process of the optical path shortening structure, a forming process of the reflection coating and a forming process of the configuration. Lastly, the process of assembling the mirror and the slider is included in the first method of manufacturing the near-field optical head.
Therefore, according to the first method for manufacturing the near-field optical head, the near-field optical head related to the present invention can be manufactured easily. In addition, as the method for forming the mirror and the slider uses photolithography or micromachining technology, mirrors and sliders having uniform performances can be produced in a large quantity.
Further, the second method for manufacturing the near-field optical head related to the present invention is a method including a process of fixing or forming the light propagating medium in the method for manufacturing the near-field optical head.
Therefore, the light propagating medium is fixed on the substrate on which is formed the slider or the mirror so that the intensity of the light emitted to the minute structure is made stable resulting in that the intensity of the light emitted from the minute structure is made stable.
Further, the third method of manufacturing the near-field optical head related to the present invention is a method characterized in that a forming process of a thin film waveguide is included in the forming process of the mirror or the slider.
Therefore, the light propagating medium can be made by means of a photolithography process so that the method for manufacturing the near-field optical head becomes easy for mass production.
Further, the fourth method of manufacturing the near-field optical head related to the present invention is a method characterized in that the process of forming a groove or a protruding for fixing the optical components is included in the method for forming the mirror.
Therefore, the mirror can be positioned to facilitate the assembly thereof and the near-field optical head capable of generating a near-field light of great intensity with stability can be provided.
Further, the fifth method for manufacturing the near-field optical head related to the present invention is a method characterized in that the method includes a grinding process of the tip of the optical fiber in parallel with the optical axis so as to sharpen the tip of the optical fiber.
Therefore, it is easy to arrange the tip of the optical fiber close to the mirror so as to provide a near-field optical head generating a near-field light of great intensity.
Further, the sixth method of manufacturing the near-field optical head related to the present invention is a method characterized in that the method includes a process of diagonal machining of the tip of the optical fiber to form a reflection coating on the diagonally machined surface thereof.
Therefore, the mirror and the light propagating medium can be made integrally and its manufacturing process can be simplified while the number of the components can be reduced so that a cheap near-field optical head with a uniform performance and less faulty components can be provided.
Further, the seventh method of manufacturing the near-field optical head related to the present invention is a method characterized in that the method includes a machining process of the tip of the optical fiber in a lens shape for concentrating the emitted light from the optical fiber onto the minute structure.
Therefore, the spot diameter of the emitted light from the optical fiber on the minute structure is reduced so that a near-field optical head generating near-field light of great intensity from the minute structure can be provided.
In addition, the fifteenth near-field optical head related to the present invention comprises a light propagating medium, a mirror for reflecting the light emitted from the light propagating medium, a minute structure arranged along the propagating direction of the light reflected back by the mirror, characterized in that the light propagating medium, the minute structure and the mirror are integrally supported by a load applying suspension arm to compose a part of a slider that makes a spacing between the recording medium and the minute structure in accordance with a balance between the load and the flying force acquired by means of the relative motion to the recording medium.
Therefore, the light propagating medium can be arranged at any given position along the thickness direction of the slider according to the condition of the emitted light from the light propagating medium so that the intensity of the light incident on the minute structure and the light emitted from the minute structure can be increased.
Further, the sixteenth near-field optical head related to the present invention is characterized in that the core part for transmitting light in the light propagating medium is arranged at a position biased toward the recording medium.
Therefore, the distance between the light emitting edge of the light propagating medium (the position of the core part in the end face of the light propagating medium) and the recording medium can be shortened further and the intensity of the light irradiated upon the recording medium can be increased.
Further, the seventeenth near-field Optical head related to the present invention is characterized in that the light propagating medium composes a part of a slider and at the same time at least a part of a suspension arm.
Therefore, losses due to the connection between the light propagating medium composing the slider and other light propagating medium for the light incident on the former light propagating medium is eliminated so that the light transmission efficiency is improved and the intensity of the light emitted the light propagating medium becomes large. Therefore, the intensity of the near-field light generated by the minute structure can be increased.
Further, the eighteenth near-field optical head related to the present invention is characterized in that the substrate provided or mounted with the mirror is constructed such that the mirror composes a part of a slider and at the same time the substrate composes at least a part of a suspension arm.
Therefore, the substrate provided or mounted with the mirror has a large area where the light propagating medium can be formed and so the restriction on the construction of the light propagating medium becomes small. As a result, the intensity of the propagated light can be transmitted in a stable and highly effective condition and by extension the intensity of the near-field light generated by the minute structure can be increased.